Ubuntu Studio CD image build failure

dediff for plucky

debdiff for noble

debdiff for noble

Looking at this for livecd-rootfs.

For livecd-rootfs plucky, I'm marking this bug "Won't Fix" as I don't see the scenario where we're reissuing an ISO. Please update this bug if I'm off the mark here.

What's going on with questing? ISO builds pass there for instance, where I would expect similar changes to be needed.

Uploaded livecd-rootfs for noble. As Michael noted, this bug should be updated for the SRU template.

I need to look at Plucky and Questing. I think they're currently pulling in the generic kernel which is why we don't see the failure. But that feels wrong.

lowlatency-kernel uploaded for noble. further uploads needed to satisfy the "Development Release Fixed First" requirement.

Ubuntu Studio switched to the generic kernel starting with Oracular. We added boot menu entries to make it a lowlatency kernel starting with Oracular, probably similar to what is being accomplished by the lowlatency-kernel package.

Hence why you're not seeing issues beyond Noble for this.

There is already a livecd-rootfs upload in noble-proposed, fixing LP: #2069391, which still needs verification.

1. https://launchpad.net/ubuntu/+source/livecd-rootfs/24.04.90

Hello Juerg, or anyone else affected,

Accepted livecd-rootfs into noble-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/livecd-rootfs/24.04.92 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-noble to verification-done-noble. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-noble. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Hello Juerg, or anyone else affected,

Accepted lowlatency-kernel into noble-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/lowlatency-kernel/1.3~24.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-noble to verification-done-noble. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-noble. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Status changed to 'Confirmed' because the bug affects multiple users.

Triggered an ubuntustudio livefs build using noble-proposed which now passes:

https://launchpad.net/~juergh/+livefs/ubuntu/noble/ubuntustudio/+build/820146

From the build log:
Get:87 http://archive.ubuntu.com/ubuntu noble-proposed/universe amd64 lowlatency-kernel amd64 1.3~24.04.1 [2142 B]
Get:161 http://ftpmaster.internal/ubuntu noble-proposed/main amd64 livecd-rootfs amd64 24.04.92 [130 kB]

This bug was fixed in the package lowlatency-kernel - 1.3

---------------
lowlatency-kernel (1.3) questing; urgency=medium

  * Skip update-grub if in a chroot (LP: #2119012)

 -- Juerg Haefliger <email address hidden> Tue, 29 Jul 2025 17:33:19 +0200

folks, correct me if I'm wrong, but the patch fixes only problem #2.

this package still calls update-grub unconditionally and breaks MAAS images.

The check that was added was looking for the grub config file, and if update-grub exists. Are this criteria met in what you described in comment #17?

We need 3 tests according to the test plan, and only one was done (in comment #15). Reverting verification flags.

We can only test the full pipeline once all packages are released.

I cannot test #2 and #3 without CD images which I won't get until the packages are released and official livefs are built.

> Ubuntu Studio switched to the generic kernel starting with Oracular. We added boot menu entries to
> make it a lowlatency kernel starting with Oracular, probably similar to what is being accomplished
> by the lowlatency-kernel package.

I think you still need changes to make the ISO boot kernel lowlatency. Otherwise 'Try Ubuntu Studio' will run with generic and not lowlatency settings.

Similar to: https://git.launchpad.net/~juergh/debian-cd/+git/ubuntu/commit/?id=69635ea048f8d62e701babdfbb306c12107fab2d

FWIW, I've built an ISO image locally using noble-proposed plus the debian-cd changes and verified:

1. Booted a VM from the ISO, selected 'Try Ubuntu Studio' and verified that the running kernel is lowlatency:
$ cat /proc/cmdline
BOOT_IMAGE=/casper/vmlinuz --- quiet splash preempt=full rcu_nocbs=all

2. Installed Ubuntu Studio, rebooted and verified the running kernel is lowlatency:
$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-6.14.0-27-generic root=UUID=3c80871f-b3fa-410e-994c-7d0eba21333d ro quiet splash preempt=full rcu_nocbs=all threadirqs vt.handoff=7

This is as much verification as I can do using an unofficial and locally built ISO.

please disregard my comment in #17, I looked only at the linked MPs, I didn't notice the patch in #2

Juerg,

We already have https://git.launchpad.net/ubuntustudio-default-settings/tree/etc/default/grub.d/ubuntustudio.cfg

> We already have https://git.launchpad.net/ubuntustudio-default-settings/tree/etc/default/grub.d/ubuntustudio.cfg

This has no effect on the running ISO kernel.

# mount questing-desktop-amd64.iso tmp/
mount: tmp: WARNING: source write-protected, mounted read-only.
# cat tmp/boot/grub/grub.cfg | grep -A4 'Ubuntu Studio'
menuentry "Try or Install Ubuntu Studio" {
 set gfxpayload=keep
 linux /casper/vmlinuz --- quiet splash
 initrd /casper/initrd
}
menuentry "Ubuntu Studio (safe graphics)" {
 set gfxpayload=keep
 linux /casper/vmlinuz nomodeset --- quiet splash
 initrd /casper/initrd
}

debian-cd uses hard-coded values when building grub.cfg for the ISO.

https://git.launchpad.net/~ubuntu-cdimage/debian-cd/+git/ubuntu/tree/tools/boot/questing/common.sh?id=69635ea048f8d62e701babdfbb306c12107fab2d#n1

https://git.launchpad.net/~ubuntu-cdimage/debian-cd/+git/ubuntu/tree/tools/boot/questing/boot-amd64?id=69635ea048f8d62e701babdfbb306c12107fab2d#n129

This bug was fixed in the package lowlatency-kernel - 1.3~24.04.1

---------------
lowlatency-kernel (1.3~24.04.1) noble; urgency=medium

  * Backport 1.3 from plucky
    - Skip update-grub if in a chroot (LP: #2119012)

 -- Juerg Haefliger <email address hidden> Tue, 29 Jul 2025 17:33:19 +0200

This bug was fixed in the package livecd-rootfs - 24.04.92

---------------
livecd-rootfs (24.04.92) noble; urgency=medium

  * Temporarily revert the 24.04.90 changes. We wish to validate only
    24.04.91 for Ubuntu 24.04.3 point release.

livecd-rootfs (24.04.91) noble; urgency=medium

  * Fix lowlatency kernel flavour name (LP: #2119012)

livecd-rootfs (24.04.90) noble; urgency=medium

  [ Chad Smith ]
  * Override cloud-init.service in /etc so as to not invalidate debsums
    (LP: #2069391)
  * Update the overridden copy of cloud-init.service

 -- Dan Bungert <email address hidden> Thu, 31 Jul 2025 11:27:41 -0600

Hello Juerg, or anyone else affected,

Accepted lowlatency-kernel into plucky-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/lowlatency-kernel/1.3~25.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-plucky to verification-done-plucky. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-plucky. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

I cannot test this with an ubuntustudio livefs, it doesn't seed the lowlatency-kernel package in Plucky. Instead, I created a Plucky chroot and manually installed the lowlatency-kernel package from release (to confirm the issue) and then from proposed to verify the fix.

1. Confirm the issue with lowlatency-kernel from plucky-release:

# sudo debootstrap plucky plucky
# sudo chroot plucky
# apt-get download lowlatency-kernel
Get:1 http://archive.ubuntu.com/ubuntu plucky/main amd64 lowlatency-kernel amd64 1.2 [1928 B]
Fetched 1928 B in 0s (4680 B/s)

# dpkg --force-all -i lowlatency-kernel_1.2_amd64.deb
Selecting previously unselected package lowlatency-kernel.
(Reading database ... 12785 files and directories currently installed.)
Preparing to unpack lowlatency-kernel_1.2_amd64.deb ...
Unpacking lowlatency-kernel (1.2) ...
dpkg: lowlatency-kernel: dependency problems, but configuring anyway as you requested:
 lowlatency-kernel depends on kernel-supports-lowlatency-bootargs; however:
  Package kernel-supports-lowlatency-bootargs is not installed.

Setting up lowlatency-kernel (1.2) ...

Configuration file '/etc/default/grub.d/99-lowlatency.cfg', does not exist on system.
Installing new config file as you requested.
/var/lib/dpkg/info/lowlatency-kernel.postinst: line 13: update-grub: command not found
dpkg: error processing package lowlatency-kernel (--install):
 installed lowlatency-kernel package post-installation script subprocess returned error exit status 127
Errors were encountered while processing:
 lowlatency-kernel

2. Verify the lowlatency-kernel from plucky-proposed

# Uninstall broken lowlatency-kernel
# Add plucky-proposed to apt sources.list
# apt-get download lowlatency-kernel/plucky-proposed
Get:1 http://archive.ubuntu.com/ubuntu plucky-proposed/main amd64 lowlatency-kernel amd64 1.3~25.04.1 [2122 B]
Fetched 2122 B in 0s (17.3 kB/s)

# dpkg --force-all -i lowlatency-kernel_1.3~25.04.1_amd64.deb
Selecting previously unselected package lowlatency-kernel.
(Reading database ... 12859 files and directories currently installed.)
Preparing to unpack lowlatency-kernel_1.3~25.04.1_amd64.deb ...
Unpacking lowlatency-kernel (1.3~25.04.1) ...
dpkg: lowlatency-kernel: dependency problems, but configuring anyway as you requested:
 lowlatency-kernel depends on kernel-supports-lowlatency-bootargs; however:
  Package kernel-supports-lowlatency-bootargs is not installed.

Setting up lowlatency-kernel (1.3~25.04.1) ...

Configuration file '/etc/default/grub.d/99-lowlatency.cfg', does not exist on system.
Installing new config file as you requested.

This bug was fixed in the package lowlatency-kernel - 1.3~25.04.1

---------------
lowlatency-kernel (1.3~25.04.1) plucky; urgency=medium

  * Backport 1.3 from questing
    - Skip update-grub if in a chroot (LP: #2119012)

 -- Juerg Haefliger <email address hidden> Tue, 29 Jul 2025 17:33:19 +0200

The verification of the Stable Release Update for lowlatency-kernel has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.